This invention relates to a fiber processing machine such as a carding machine or a roller card unit and is more particularly directed to a sliver forming device including a roll unit and a web trumpet followed by calender rolls. The roll unit may be, for example, a doffer, a stripping roll and/or crushing rolls. The web trumpet receives the web and densifies it to form a sliver which then passes through a calender roll pair. Between the roll unit and the web trumpet a web guiding element is arranged which has an approximately triangular configuration.
U.S. Pat. No. 3,339,245 describes an arrangement in a carding machine where a shaping or folding section is arranged after the doffer. The section is composed of two serially arranged web trumpets between which a pressing roll pair is disposed. The doffer, the web trumpets and the pressing roll pair are each spaced from one another. The axis of the doffer and the pressing rolls are oriented parallel to one another. The width of the outlet of the web trumpet is greater than its height; the long, wide axis of the discharge region is parallel to the axes of the doffer and the pressing rolls. The wide, thin fiber web taken off the doffer passes through the first web trumpet which halves the original web width by folding flanking web portions over the central half width of the web. After the thus-thickened web exits the first web trumpet, it passes through the nip of the pressing roll pair to press the web flat. As the material is discharged by the pressing roll pair, its width is approximately one-half and its thickness approximately twice the fiber web as it was taken off the doffer. Thereafter, the fiber web passes through a second web trumpet which again halves the width of the web. The web reduced in this manner which exits the second trumpet as a strip, is stronger than the original web which was densified into a narrower and thicker strip. The web taken off the doffer has a number of folds (transverse waves) along its width due to the triangular gathering of the running web in the direction of the web trumpet. At the outlet of the trumpet, because of the small outlet height, the folds are compressed from above while the folds are laterally only gathered because of the large outlet width of the trumpet. In the nip of the subsequent pressing rolls the folds are fully crushed in the direction of their amplitude (height direction). It is a disadvantage of such a prior art arrangement that it is complex and expensive and furthermore, a deliberate guidance of the web upstream of and in the web trumpets is not provided so that a disturbance-free, secure introduction into the web trumpets is not possible. It is a further drawback that the web strip discharged by the first web trumpet and the pressing roll pair as well as the web strip discharged by the second web trumpet have a substantially weakened strength in the central regions. As a result, the strip disadvantageously tears in the longitudinal center during further processing in case outwardly directed forces are applied to the edges of the material. Such irregularities are particularly troublesome when the strip constitutes an initial or intermediate product for final products such as articles of hygiene.
It is an object of the invention to provide an improved device of the above-outlined type from which the discussed disadvantages are eliminated and which, in particular, is structurally simple and makes possible the making of sliver having a significantly more uniform fiber distribution and increased strength.
This object and others to become apparent as the specification progresses, are accomplished by the invention, according to which, briefly stated, the fiber processing machine includes an arrangement for producing a running fiber web having a width extending perpendicularly to the running direction; a roll unit having a roll axis and a roll surface engaging the running web; a web guiding element disposed downstream of the roll unit for laterally gathering the web for reducing the width thereof; and a web trumpet disposed downstream of the web guiding element. The web trumpet has an outlet opening for discharging the running web. The outlet opening has an outlet height and an outlet width greater than the outlet height. The outlet width is oriented to the roll axis at an angle other than zero for reorienting the width of the web during run thereof from the roll unit to the outlet opening. A calender roll pair is disposed downstream of the web trumpet.
As a result of the measures according to the invention, a sliver having a significantly more uniform fiber distribution over its cross section may be obtained. The sliver has a greater strength in the transverse direction and thus better resists laterally outwardly directed forces. It is a particular advantage of the invention that, in contrast to known arrangements, a relocation of the separating location of the strip from the middle of the width to the middle of its thickness is achieved. Also, by virtue of the invention, a higher output speed is feasible and a processing of fiber material with a higher short-fiber proportion is possible.